The invention relates generally to broadcast audience measurement, and, more particularly, to methods and apparatus for identifying the source of a signal selected by an audience member in a statistically selected dwelling unit via an intermediate frequency probe.
It is well known that broadcast ratings (e.g., television and radio program ratings) are developed by companies such as Nielsen Media Research by monitoring the usage patterns of audience members in statistically selected homes. By developing accurate readings of the programs received by the members of theses homes, it is possible to develop similarly accurate indications of the size and demographic composition of the audience in general. To ensure the ratings developed are as accurate as possible, it is important to ensure accuracy in identifying the programs received by the monitored audience members. To ensure that the monitoring process does not inconvenience the monitored audience by requiring members to monitor their own usage, electronic monitoring of the signals received by the receivers of the audience members has long been preferred.
The use of a super-heterodyne tuner in which a user-selected local oscillator frequency is heterodyned with a received RF signal to generate a fixed-frequency band of tuned signals that is input to an intermediate frequency (hereinafter I.F.) amplifier has long been known in the radio signaling arts.
Watanabe, U.S. Pat. No. 3,803,349, discloses a television audience measurement system wherein successive sound I.F. signals taken from a monitored television receiver are compared with respective sound I.F. signals taken from a slaved television tuner of the measurement apparatus. Watanabe does not teach the use of video I.F. signals for making this comparison, nor does it disclose the use of a non-invasive probe or pick-up for acquiring an I.F. signal from the monitored receiver. Watanabe also fails to disclose a method or apparatus for injecting an I.F. recognition signal into the monitored receiver.
Azuma, U.S. Pat. No. 5,678,214, and Eum, U.S. Pat. No. 5,633,690, disclose arrangements for adjusting the levels of I.F. signals in a receiver.
Those in the field of broadcast audience measurement have long realized the advantages of making tuning measurements on a sampled receiver in a minimally invasive manner (i.e., in a manner that seeks to avoid opening the enclosure of a monitored receiver and that seeks to avoid making a direct metallic connection to the circuitry of the receiver). Such minimally invasive approaches are advantageous because they minimize the chance of damaging a panelist""s receiver, and they decrease the time required for installation of equipment within a statistically selected dwelling. A well-known approach to achieving this goal has been the use of local oscillator measurements. For example, Freeman, U.S. Pat. No. 2,892,885, discloses a local oscillator measurement approach in which a signal which is representative of the local oscillator frequency generated by a measured receiver is acquired by a probe or antenna that does not make direct electrical contact with the receiver. Another known non-invasive approach is that of acquiring a video signal by placing an appropriate antenna or pick-up adjacent a cathode ray tube (CRT) associated with the monitored television receiver. This latter approach is taught by Chan et al., U.S. Pat. No. 5,889,548, which is assigned to the same assignee as is the present invention, and which is incorporated herein in its entirety by reference.
A tuner measurement approach that is also relevant to the present invention, but that heretofore has not been available as a non-invasive measurement of a sampled television, is that of signal injection. Porter, U.S. Pat. No. 4,044,376, discloses a tuning measurement approach in which a characteristic RF signal is injected at the antenna terminals of a measured receiver during the vertical blanking period of the television signal that is being displayed. After sequentially injecting the RF signal at each of the channels to which the receiver could be tuned, the channel that is actually tuned on the television set is identified by making an electrical connection to a video test point and observing when the injected signal appears at the output of the tuner. To avoid interference with the television signal being viewed, Porter injects the signal during the vertical blanking interval. A shortcoming of the Porter approach is that, in a common measurement situation in which two receivers in a sampled dwelling are served by the same cable, a recognition signal injected at the antenna terminals of one of the receivers could also be received at the other receiver where it would generate visible interference if that other receiver was tuned to a different signal source. This problem has been solved by using a directional coupler to isolate the monitored receiver from any other receiver serviced by the same antenna cable.
Another signal injection arrangement, which involves replacing a sampled tuner with one modified by the addition of measurement apparatus, is taught by Mostafa et al., U.S. Pat. No. 5,495,282. In the Mostafa et al. arrangement the characteristic signal is injected, detected, and stripped in a separate apparatus interposed between the external tuner and a television set.
In accordance with an aspect of the invention, a method is provided for determining whether a signal of a program tuned by a tuner of a receiver is being output by an output device of the receiver. The method comprises the steps of: radiating an intermediate frequency recognition signal from an intermediate frequency probe disposed adjacent the tuner of the receiver; developing a representation of a signal output by the output device of the receiver with an output probe and examining a representation of a signal output by the output device of the receiver to determine if the recognition signal is present in the signal.
In some embodiments, the method also includes the steps of: detecting a second signal output by the output device of the receiver; and determining a time interval corresponding to a non-viewable portion of the second signal by examining a representation of the second signal. In such embodiments, the step of radiating an intermediate frequency recognition signal is performed during the time interval determined from the second signal. In some such embodiments, the time interval corresponds to an overscan region of a viewable picture on the output device, and/or the representation of the second signal comprises the second signal.
In some embodiments, the representation of the signal comprises the signal.
In some embodiments, the intermediate frequency recognition signal is radiated at a predetermined frequency offset from a tuned frequency by less than a width of a broadcast television channel.
Optionally, the output device is a display device and the representation of the signal is acquired from a video probe disposed adjacent the display device.
In some embodiments, the method also includes the steps of: developing a representation of a tuned intermediate frequency signal radiated by the tuner by parasitically detecting the tuned intermediate frequency signal with the intermediate frequency probe; obtaining a representation of a direct input signal; and comparing the direct input signal representation with the signal representation developed by the output probe, and comparing the tuned intermediate frequency signal representation with the signal representation developed by the output probe to determine whether the signal displayed on the output device is the tuned intermediate frequency signal or the direct input signal.
In accordance with another aspect of the invention, an apparatus is provided for determining if a signal output by a receiver having a plurality of local inputs was tuned by a tuner of the receiver. The apparatus includes an intermediate frequency probe disposed in proximity to the tuner of the receiver to receive an intermediate frequency signal radiated by the tuner. It also includes a demodulator in communication with the intermediate frequency probe to demodulate the intermediate frequency signal received from the intermediate frequency probe to develop a first test signal. Additionally, the apparatus is provided with an output probe located to develop a second test signal representative of the signal output by the receiver; and a comparison circuit for comparing the first and second test signals to determine if the signal output by the receiver was tuned by the tuner.
In some embodiments, the output probe comprises a video probe disposed in proximity to a display device of the receiver and the second test signal comprises a video signal.
In some embodiments, the apparatus also includes an intermediate frequency signal generating circuit in communication with the probe to selectively radiate a recognition signal from the intermediate frequency probe. In some such embodiments, the apparatus is further provided with an injected signal detector in communication with the output probe for examining the second test signal developed by the output probe for the presence of the intermediate frequency signal.
In some embodiments, the output probe comprises a microphone and the second test signal comprises an audio signal.
In some embodiments, the comparison circuit comprises a decoder for decoding a first ancillary coded message from the first test signal and for decoding a second ancillary coded message from the second test signal; and a logic circuit for comparing the first and the second ancillary coded messages.
In some embodiments, the comparison circuit comprises a program signal extractor for extracting a first program signature from the first test signal and for extracting a second program signature from the second test signal; and a logic circuit for comparing the first and the second program signatures.
In some embodiments, the comparison circuit compares a representation of a direct input signal from at least one of the local inputs with the second test signal to determine if the signal output by the receiver originated at the at least one of the radio frequency inputs. In some such embodiments, the apparatus also includes a library of program signatures and the comparison circuit compares a program signature of at least one of the first test signal, the second test signal and the representation of the direct input signal to at least one signature stored in the library to identify a program associated with the signal output by the receiver.
In accordance with another aspect of the invention, a combination of a broadcast audience measurement circuit for monitoring programs output by a receiver and an intermediate frequency probe for acquiring a replica of a signal tuned by a tuner of the monitored receiver is disclosed. The intermediate frequency probe of the combination includes a wire loop; a capacitor attached across the wire loop so as to form a circuit element tuned to the intermediate frequency of a monitored receiver; and a shielded coaxial cable having a first end coupled to the wire loop and a second end which is adapted to connect to an intermediate frequency signal processing circuit. The intermediate frequency probe also includes means for attaching the probe to an external surface of the monitored receiver in proximity to the tuner.
In some embodiments, an outer conductor portion of the coaxial cable comprises a direct metallic connection to a reference electrical ground of the monitored receiver, and the intermediate frequency probe has no other direct metallic connection to the monitored receiver.
Other features and advantages are inherent in the apparatus claimed and disclosed or will become apparent to those skilled in the art from the following detailed description and its accompanying drawings.